The inability to control chemical spray drift and the misapplication of chemicals caused by spray drift is an ongoing concern, especially when applying such products from the air by means of aircraft. Such lack of control and spray drift removes some of the chemicals from the intended target(s) and deposits them in or on unplanned or undesirable locations or targets. Off-target chemical spray drift deposits can temporarily or permanently injure or damage individuals, susceptible vegetation, wildlife, air and water supplies, and other similar recipients. Although such chemical spray drift may not be completely eliminated, the use of proper equipment and application techniques may minimize unplanned or undesirable chemical spray drift deposits.
In contrast to the desirability of eliminating or minimizing certain chemical spray drift, for row crop spraying for example, applying mosquito insecticides requires controlled drift spraying. Particularly in the case of mosquito control, the need to measure and evaluate wind speed and wind direction at a particular reference level or application height is critical for controlling spray drift (allowing drift to occur in a controlled manner) and thereby increasing safety in such chemical application from an aircraft. Similarly, it is also important to know what the stability of the atmosphere is for the given location. The ability to predict aircraft upwind offset distance based on spray drift modeling and the boundaries of where the spray will settle is desirable for an efficient and successful aerial chemical application.
Determining critical parameters of wind speed and wind direction at various reference levels or flight application heights is required in controlling and in eliminating or minimizing chemical spray drift deposits, in recording meteorological and flight conditions at a particular location, and in predicting spray drift. Reference levels or chemical application heights vary with particular applications. For example, a nominal ground level or near ground level chemical application height for row crop chemical spraying is typically about 10 to 20 feet above ground level. Forest application requires a nominal chemical application height of about 70 to 100 feet above ground level. Insecticide application, such as mosquito control, requires a nominal chemical application height of about 150 to 500 feet above ground level. Such information also provides the aircraft pilot the data needed to determine how and whether to apply spray chemicals based on application guidelines or labeling requirements governing such spray applications. Knowledge of such parameters is critical at each reference level in order to specifically and effectively control and predict chemical spray drift applied from the air.
Previous approaches exist that attempt to control off-target chemical spray drift. Additionally, several devices have been developed to determine, measure, indicate, and/or display aircraft air speed, the effects of crosswinds on a vehicle, the mean wind speed with respect to the ground of an aircraft, the ground speed of an aircraft, and the difference between air speed and ground speed of a motor vehicle, by the art disclosed in U.S. Pat. No. 5,546,799. This patent provides for a device for monitoring the draft created by a lead vehicle so that a trailing vehicle can be kept at an optimal distance from the lead vehicle to maximize gas or fuel mileage by measuring and displaying the difference between the air speed and ground speed of such motor vehicle to determine headwind or tailwind magnitudes.
Another method (U.S. Pat. No. 5,091,871) provides for determining the speed of the mean wind with respect to the ground during the flight period of an aircraft. Another method (U.S. Pat. No. 5,025,988) provides an aircraft spray distribution system including a nozzle design that does not mist the spray and cause off-target drift. Other methods (U.S. Pat. Nos. 6,669,105 and 6,926,211) provide for a mobile, ground-based, closed-loop system for delivering insecticide spray that focus on regulation of insecticide particle size and of amounts of insecticide sprayed. Another method (U.S. Pat. No. 6,799,740) provides for a system for controlling and effecting an appropriate or effective application or distribution of chemicals from an aircraft onto a ground target based on weather parameters at ground level and at aircraft level. In this patent ('740), the application equipment must be near the site of such parameter measurement to obtain valid reliability. Additionally, such ground-based equipment provides parameters that are only valid for relatively short spatial distances. Finally, parameter calculations based on measurements at a single-point-in-time-based system, as in this patent ('740), can be misleading, particularly under variable wind conditions. These devices and methods and the devices and methods referenced therein may not necessarily provide accurate or reliable wind speed and wind direction parameters under certain conditions during an aircraft flight. The present invention provides high reliability of critical parameter measurement since its measurement equipment is always on board the aircraft and its method uses no ground-based instrumentation. The present invention obtains its measurements over a reasonable time span and processes its data simultaneously to minimize the sum of the errors squared. Further, the other devices and methods do not also necessarily provide a means for measuring the lift reserve of an aircraft or a means for determining or recording accurate atmospheric stability or instability for a given spatial location as does the present invention. More importantly, those devices and methods do not provide such critical information for providing an aircraft pilot the ability to specifically predict the behavior of spray drift or to specifically minimize chemical spray drift, to predict spray drift or trajectory, to predict aircraft upwind offset distance and flight path, or to allow automatic chemical spray cutoff and likewise do not involve resultant methods of increasing safety in airborne chemical application as does the present invention.
Although known methods exist to determine moving vehicle air and ground speeds and to distribute chemicals from the air, it remains a significant goal of those skilled in the art to devise a simple method and system to specifically control chemical spray drift application from the air, to limit such chemical spray application outside a desired application zone, to allow automatic spray cutoff, to predict spray drift behavior, to predict aircraft upwind offset distance and flight path, and to thereby increase safety in such chemical application from an aircraft. The present inventors have designed a method and system for these purposes.